[unreadable] This Shared Instrumentation Grant proposal is for the acquisition of a modern commercial CW and Pulsed EPR spectrometer for use by San Francisco Bay area EPR users targeting biological metal and radical centers. The proposed instrument, a Bruker EleXsys 580, offers state-of-the-art performance for both continuous wave (CW) and pulsed EPR experiments. In addition to the standard X-band frequency (9.4 GHz), we propose to add the Q-band (35 GHz) option for both CW and pulsed operations. We are also proposing both CW and pulsed electron nuclear double resonance (ENDOR) capabilities. Low temperature cryostats are included for the different resonator combinations. A generous matching commitment by the Principal Investigator's institution, UC-Davis, allows us to propose these crucial options (Q-band, ENDOR, cryogenics). This instrument will provide access to a variety of modern advanced EPR methods for a wide array of NIH funded groups examining paramagnetic metal or radical centers, either naturally occurring in enzymes or added as spin probes. [unreadable] [unreadable]